The purpose of this project is to study the molecular aspects of the killing of nucleated cells by immune attack; in particular the interaction of antibody (class, affinity, etc.) and complement with one another and with the cell surface. BIBLIOGRAPHIC REFERENCES: Boyle, M.D.P. and Ohanian, S.H.: Quantitation of antibody-complement mediated lysis of tumor cells. J. Immunol. Methods 15: 135-146, 1977. Boyle, M.D.P., Ohanian, S.H. and Borsos, T.: Studies on the terminal stages of antibody-complement mediated killing of a tumor cell. III. Effect of membrane active agents. J. Immunol. 117: 106-109, 1977.